Radio signaling system



Nov. 6, 1928. l1,690,250

A. w. sAUNDERs RADIO S IGNALING SYSTEM Filed July 21, 1925 EMP-... WIW M ai. n

N apn//o/u/y ffy by @mw-A7714 possible'to use transformers for coupling Y Patented Nov. s, 192s.

: UNITEDI STATES PATENT .oFricE.

ALFRED W. sAUNDEIis, 'orjiironNfrvnniaoN, NEW YORK, AssiGNOn To WESTERN ELEO- i INCORPORATED, ONNEW YORK, N. Y., A CORPORATION OF NEWl TRIC COMPANY, YORK.

RADIO SIGNALING SYSTEM.

application ined my 2i, i925. serial No. 44.989.

This invention relates to radio signaling systems andV more particularly to apparatus for couplingspace discharge tubes.4

It is usually found, in dealingrr with high frequency repeaters and amplifiers, that each element reacts uponrevery other with which it is associated and that it is often difficult to couple one element to another Withoutpro- Yducing effects Whose occurrence is not readily predictable and which are vdiilicultto control. F or example, in radio receiving systems employing high frequency amplifiers, it may be several space discharge devices in tandem and to secure a transmission characteristic having noiserious irregularities; But when it is attempted tocouple another element suclias a localheterodyne oscillator by means of a coil xinductively associated `with the transformer for coupling the circuits of the discharge dc.- vices, irregularities of. a detrimental char acter are generally introduced. lThis is because of' the mutual reaction between the coupled circuit-s.

The use of high frequency ampliiierses# pecially in connection with heterodyne rcceiving: circuits, is desirable because of thek advantageswhich result. Among these ad- ,vantages are the increased amplification and selectivity which may` be Obtained, with a consequentV reductionof interference from static disturbances and Without greatly` increased liability ofdistortion caused by singi `ingoi-.parasitic oscillations. The problem of properly coupling high frequency` am-v plifiers and oscillators with each other and with other, portions of their associated circuits is thus seen to be of considerable im-V portance.

Itis Van object of'this invention towini ductively ,couple` a source of local Waves toy a i A furtheriobject is tosimplify the coupling` Wave transmission path, including high `frequency amplifiers, .andl to maintain a desirable transmission characteristic 4for-,the

Wave transmission path. l j

A furtl cr objcctisto combine signal Waves and `local wavesvin av transmission path and to pre-vent' detrimental eifects upon the transmission characteristic of the path.

An additional object is to prevent the radiation of, energy from` a local oscillator inductively coupled to a circuit including an antenna.` i i' Theinvention y `comprises A broadly, a

high` frequency` circuit including repeaters ing input and output circuits coupled for the generationof oscillations, all couplings being c'ilected by a'siiigle `transformer including a plurality of windings arranged coa-Xiall-y and so positioned with respect to each other that one repeater mayV constitute a high frequency amplifier, and is arranged between the oscillai tor an an antenna., to prevent the radiation of Waves generated by thc local oscillator. The ti'ansforiiier windings may be of any desired form, for example, annu-lar. or` colenoidal. i.

Tlieinvention is` illustrated in the draw,n

.ings `.therein Fig. 1 shows a general applica- Vtion of the invention to the coupling of rz?-y aeaters. Y Fig. 2 is a graphillusti-ating the transmission characteristic of a.. circuit including .the invention.

Fig. 3 illustrates-a radio receiving circuit including the coupling arrangcnientof the invention.

The invention will first be described with reference to'Fig. l... A space discharge tube which represents, for example, a high frequency amplifierincludes the customary electrodes and associated. circuits wherein an inductance ll'lias a' portion included in an input circuit connected to tliegcontrolV electrode and cathode, and a transformer` l2 has a primary Winding 2O connected to` the anode of the tube 10. Condenser lglbalances the inherent capacity of the electrodes of the tube.

the transmis` to each other and coupled in tandem and another repeater havlA secondaryivinding 1li of i,

transformer 12 is included in a circuit connected to the. control electrode ofa repeater tube 15 which` may be an amplifier or ade-A tector or the like.` f

A `third space discharge tube 16 has an input circuit connected to its control electrode and cathode including another winding 17 of the transformer 12. An adjustable condenser 18 is shown connected in shunt to this winding to form a resonant circuit therewith. An output circuit for tube 16 is connected to its anode and includes the fourth winding 19 of transforn'ier 12. The windings 14, 17, 19 and 2O of transformer 12 are all coupled together, thus the windings 17 and 19 couple the input and output circuits of tube 16 to each other and to the tandem arrangement' of repeaters 10 and 15,which are in turn coupled by the windings 2() and 14. The resonant element 17--18 determines the frequency of oscillations, generated by the circuit including tube 16, which are produced by virtue of the coupling between its input. and output circuits afforded by transformer 12.

The winding 17 of transformer 12, which is connected to the grid of tube 16, is positioned adjacent to the winding 14 connected to the control electrode of tube 15 and winding 19 is positioned adjacent the winding 17, whereas winding 2O is positioned adjacent to windingT 14. Windings 19 and 2O are therefore remote from each other and the mutual inductance between them is made small so that undesirable reaction of the oscillator on the amplifiers is avoided.

The inductance 11 may represent. an antenna such as a loop antenna and by interposing the uni-laterally conducting tube 10 between the antenna and the oscillator 16 the radiation of waves produced by the oscillator from the antenna is prevented. It is to be understood that the inductance 11 may be coupled to an ordinary open antenna.

A specific form of transformer which was found to function without introducing undesired irregularities in the transmission characteristic of the associated circuit consisted of windings of annular shape having an outside diameter of two inches, an inside diameter of one inch and a thickness of 3/64 inches. findings corresponding to windings 2O and 11 of Fig. 1, included approximatelyv 170 and 19() turns, respectively, and were spaced with their adjacent sides 5/36 inches apart. lindings corresponding to 17 and 19 of Fig. 1 included approximately and 50 turns, respectively, and were spaced with their adjacent sides 1,@ inches apart.

By this arrangement the coupling circuit is simplified since in the ordinary case a separate transformer or at least sep rate windings would be required for coupling the oscillator to the input circuit of tube 15. rlhe extraV transformer or windings are hereby eliminated without detriment to the transmission characteristic of the circuit.

'lhe approximate transmission characteristic obtained by using a coupling arrangement, substantially as described above, is represented by curve A of Fig. 2. This relatively smooth transmission characteristic was scoured by the. design and arrangement of the transformer windings and the advantage of the particular design specified is clearly brought out by reference to curve B of Fig. 2 which illustrates the transmission characteristic of substantially the same circuit with a different arrangement of transformer windings. The curve A. represent a transmission characteristic free of serious irregularities, i. e. substantially uniform for a definite frequency range, whereas the curve B represents a characteristic containing irregularities which would produce serious distortion.

The radio receiving circuit illustrated in Fig. 3 is of the heterodyne type and includes an antenna and an associated timing condenser 26 connected to electrodes of a space discharge tube 27 designed to amplify high frequency waves.

The mid-point of the loop 25 is connected to the cathode of tubc 27 in series with the filament of detector tube 28. One outer terminal is connected to the control electrode of tube 27 and the other outer terminal is connected by the path includingr condenser 29 to the anode of tube 27. Condenser 29 functions in a manner generally understood to compensate for inherent capacity between the grid and anode of tube 27, so that the production of parasitic oscillations in the amplifier circuit is prevented.

A space current circuit for tube 27 includes the winding 20 of transformer 12, one terminal being connected to the anode and the other connected to space current source represented by battery 30, thence to ground at the cathode of tube 27. This circuit also constitutes the alternating current output circuit of tube 27 which is coupled to the input circuit of detector 2S by the winding 1-1 having one terminal connected to the control electrode and the opposite terminal connected to the cathode of tube 28 in series with the lilaments of tubes 3, 35, ifi-1, 32, and 91.

An oscillator includes tube 35, the winding 17 of transformer 12 (.'ounected between its control electrode and cathode and the winding 19 connected between its anode and cathode; the two windings serving as a feedback coupling for the generation of oscillations. An adjustable condenser 36 is arranged in shunt to winding 17 to provide a resonant circuit for determiningr the frequency of oscillations generated by the system including tube 35. The space current circuit of tube connected toits anode and cathode. includes the winding 19 of transformer l2 in series with space current source 3U.

The transformer 12 in this figure has its circuit coupled in the manner illustrated and described in Fig. 1 and functions to provide a desirable transmission characteristic in the manner described in connection with Fig. 1.

lul:

coupled to a two sta l form no material part of the invention. The

accordingly may be arranged in any wel known manner. l p

A second detector tube 33, including the well known arrangement of grid leak resist-- ance and blocking condenser 41 in its input circuit, has this circuit coupled tothe output circuit of intermediate frequency amplifier 40. The output circuit Aof detector 33 is coupled to the input circuit of an audible frequency amplifier 34. The amplifier 34 includes terminals 42 adapted to be connected to a suitable receiving device, wire line orY the like.

In the operation of the circuits shown in Fig. 3, high frequency waves modulated in accordance with signals are received by antenna and are supplied to the input circuit of tube 27. The received waves are amplified by tube 27 and supplied through windings 20 and 14 of transformer 12 to the input circuit of detector `28. c

Oscillations are generated in the circuts associated with tube 35 by virtue of the cou- `pling between coils 17 and 19 as already mentioned. These oscillations are supplied to the input circuit of detector 28 by virtue of the coupling between coils 14 and 17.

The received waves and local oscillations are supplied to the input circuit of the detector 28 in whichfthey are combined to produce, in the output circuit, signal modulated waves of an intermediate frequency, which is preferably above the range of audibility. However, the frequency of these waves should be sufficiently low to be readily amplified by i the intermediate frequency amplifier 40. The

amplified intermediate frequency waves are detected, in the device 33, in the manner well understood and then amplified by device 34 and supplied to the device or line connectedy to terminals 42.

This invention has been described in association Vwith certain specific embodiments for the purpose of morev clearly explaining the principles of its operation and not for the purpose of defining its scope which it is understood is determined only by the appended claims.

What is claimed is:

1. In combination, an antenna, a high frequency amplifier, a detector and an oscillator,

y eachhaving an input circuitV and an output circuit, 'means for connecting the input circuit of the amplifier to the antenna, and a `transformer,havin windingsinductivel as- ,soclated for coupling the output circuit of said amplifierk to the input circuit of said de tector, for coupling the input and output circuits of said oscillator and also for cou.- pling said oscillator to said detector.

2. In a radio system comprising an antenna,

space discharge tubes, an input circuit and u an output circuit associated with each tube, a transformer having inductively associated windings for transferring energy from 'i the output circuit of one tube to the input circuit of a second tube, between the input and output circuits of a third tube to constitute an oscillator and to the input circuit of said second tube from the oscillator, whereby oscillations may be supplied to the input circuit lof the second tube but are substantially prevented from reaching the antenna.

3. In a radio system, space discharge tubes, each having input and output electrodes, input and output circuits for each tube, and a transforme-r having four annularly and coaxially positioned windings respectively included in theoutput circuit ofthe first tube, the input circuitof a second tube, and the input and output circuits of a third tube, said second winding separating said first winding from the other two windings.

4. In a radio receiving system, a high Vfrequency amplifier, a high frequency detector, and a high frequency oscillator, said amplifier, detector and oscillator including respective input and output circuits, and a t-ransformer having inductively associated windings connected respectively in the output circuit of the amplifier, in the input circuit of of said oscillator, the winding in thel output circuit of said oscillator being separated from the winding in the incoming circuit by said other two windings.

In witness whereof, I hereunto subscribe my name this 17th day of July, A. D. 1925.

ALFRED W. SAUNDERS. 

